Artifitial walls at outlet

oyvinl · February 23, 2011, 16:31

I`m simulating a centrifugal compressor and have a problem with the outlet boundary. The Outlet BC is set to "Outlet" with a mass flow. The problem is that when simulating, walls (about 0,5 % of area) are constructed to prevent flow into the domain. I know that 0,5% may not affect the solution, but still... I read that the solution is to place the outlet far away from the blade (50-100%) of the chord length.. I have placed the outlet at various distance, and are now at about 300% of chord length, but the problem remains.

Can it be a physical problem, or is this just a problem with CFX??

ghorrocks · February 23, 2011, 16:45

It looks like you have a long, thin separation. Sometimes these can take a long time to settle out. I think you just have to go longer on your outlet runner if you wish to eliminate it.

February 23, 2011, 16:31	Artifitial walls at outlet	#1
oyvinl New Member Øyvind Larsen Join Date: Feb 2011 Posts: 2 Rep Power: 0	I`m simulating a centrifugal compressor and have a problem with the outlet boundary. The Outlet BC is set to "Outlet" with a mass flow. The problem is that when simulating, walls (about 0,5 % of area) are constructed to prevent flow into the domain. I know that 0,5% may not affect the solution, but still... I read that the solution is to place the outlet far away from the blade (50-100%) of the chord length.. I have placed the outlet at various distance, and are now at about 300% of chord length, but the problem remains. Can it be a physical problem, or is this just a problem with CFX??

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February 23, 2011, 16:45		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	It looks like you have a long, thin separation. Sometimes these can take a long time to settle out. I think you just have to go longer on your outlet runner if you wish to eliminate it.